Iridium 9604 vs 9603: what is the difference?
In short
The 9604 combines SBD satellite, LTE-M cellular and GNSS in one module; both use SBD for satellite.
The Iridium 9603 is the SBD module inside many satellite IoT products, and it does satellite only. The Iridium 9604 puts satellite, cellular and positioning into a single module, and its satellite side is still SBD.
| Iridium 9603 | Iridium 9604 | |
|---|---|---|
| Satellite service | Iridium SBD | Iridium SBD |
| Per message | 340 bytes MO / 270 bytes MT | 340 bytes MO / 270 bytes MT |
| Cellular | None | LTE-M (LTE Cat M1) |
| GNSS | None (a GPS can share the board) | Built in: GPS, GLONASS, BeiDou, Galileo |
| Antennas | One (Iridium) | Two: one shared by Iridium and GNSS, one for LTE-M |
| Dimensions | 31.5 × 29.6 × 8.1 mm | 16.0 × 26.0 × 2.4 mm |
| Weight | 11.4 g | < 3 g |
| Power supply | 5.0 V ± 0.5 V | 3.8 V nominal (3.0 to 4.5 V) |
| Operating temperature | -40 to +85 °C | -40 to +85 °C |
9603 figures from Iridium's product specifications; 9604 figures from the Iridium 9604 Fact Sheet and product page.
The real difference: you decide when to use satellite
The 9603 has one path, satellite. The 9604 has both LTE-M and satellite, but it does not switch automatically — by design the developer decides: LTE-M while there is coverage and satellite when there is not, or finer routing by position, cost and power. The built-in GNSS tells the device where it is, so location can be part of that decision.
Does an existing SBD back end have to change?
Not for satellite. 9604 satellite messages are SBD, with the same size limits as the 9603 and the same delivery methods; with SBD CC, 9603 and 9604 devices use the same API. What is new is the LTE-M path: that data travels over the cellular network, not through Iridium, and your system has to receive it separately.
Moving from the 9603 to the 9604
- A new board design: the package, size and supply voltage all differ, so the 9604 is not a drop-in replacement.
- One more SIM: LTE-M needs a cellular SIM (Iridium says the 9604 development kit can be used with your own SIM card).
- Power headroom: the 9604 draws 2.5 A typical while transmitting to the satellite.
- Switching logic in firmware: when to use LTE-M and when to use satellite is up to you.
- Certification: the 9604 module holds FCC, ISED, CE-RED and UKCA plus PTCRB and GCF; a finished product still needs whatever certification the markets it is sold in require.
Which one when
- Mostly within cellular coverage, occasionally outside it (fleets, vessels in and out of port, farm machinery): the 9604, on LTE-M normally and satellite when there is no signal.
- Permanently beyond cellular coverage (mountains, at sea, remote sites) with small payloads: the 9603 is enough.
- Positioning built in, and three parts reduced to one: the 9604.
- Messages large enough for a photo or voice clip: neither — look at the Iridium Certus 9704, which uses IMT.
Sources
- Iridium 9604: Iridium 9604 Fact Sheet (June 2026); Iridium product pages for the 9604 and the 9604 Satellite IoT Development Kit.
- Iridium 9603: Iridium, 'Iridium 9603 Module' product specifications.
- SBD message sizes: Ground Control Knowledgebase, 'About SBD'.
Is the 9604 a drop-in replacement for the 9603?
No. The package, size and supply voltage differ, so the board has to be redesigned; the satellite (SBD) message format and size limits are the same.
Can SBD CC receive 9604 satellite data?
Yes, exactly as for the 9603: uplinks are forwarded to your server over HTTPS and downlinks are sent through the API.
Is there a 9604 development kit?
Yes. Iridium offers the 9604 Satellite IoT Development Kit with a Launch Pad developer board, 3,000 mAh lithium-ion battery, helical Iridium antenna and microSD card; contact N3D about availability.
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Updated 2026-10-22
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